USB Power banks
I haven’t played very much with 18650 yet but found this interesting.
and run them from salvaged 18650 cells from laptop batteries… They’ll run a little 5v microcontroller with a couple of blinkenlights approximately forever.
I can charge my cell phone or tablet at about 3A from them, my phone will top up from almost dead several times on a single charge. We should do a workshop on tearing down laptop batteries next time @DRDEMENTED brings us a stack of recyclable laptops. Many packs will have 6 or so cells in them, and frequently only one of them will be faulty.
18650 cells in big honking packs are also good for running cordless tools and electric bicycle projects.